Molecular dynamics simulations of the bulk phases of 4-cyano-4′-n-pentyloxybiphenyl

Hauptmann, Sven; Mosell, Thomas; Reiling, Stephan; Brickmann, Jürgen

doi:10.1016/0301-0104(96)00073-0

Cited by 29 publications

(21 citation statements)

References 43 publications

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“…Indeed, in a work on 4,4Ј-di-n-pentyl-bibicyclo͓2.2.2͔octane ͑5,5-BBCO͒ modeled with a UA potential, McBride et al 9 found that the order parameter reached a fairly stable value of Ӎ0.7 after about 10 ns starting from an isotropic fluid. Also, in MD ͑UA͒ simulations of the 4-cyano, 4Ј-n-pentyloxybiphenyl ͑5OCB͒ molecule, Hauptmann et al 8 did not achieve a converged P 2 value after Ӎ1.5 ns, using some starting configurations differing only in the order parameter.…”

Section: Discussionmentioning

confidence: 98%

“…7 and Table III. The measures of translational diffusion coefficients reported in literature, both experimental 20-23 and simulated, 4,5,8,10 show significant disagreement, their values depending on the experimental technique or on the model adopted. Such discrepancies are so marked that the term ''experimental dilemma'' has been used in a recent review.…”

Section: The Modified Intermolecular Potentialmentioning

confidence: 91%

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Stability of the nematic phase of 4-n-pentyl-4′-cyanobiphenyl studied by computer simulation using a hybrid model

Cacelli

Prampolini

Tani

2002

The Journal of Chemical Physics

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Section: Discussionmentioning

confidence: 98%

Section: The Modified Intermolecular Potentialmentioning

confidence: 91%

Stability of the nematic phase of 4-n-pentyl-4′-cyanobiphenyl studied by computer simulation using a hybrid model

Cacelli

Prampolini

Tani

2002

The Journal of Chemical Physics

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“…In this context, liquid crystalline (LC) materials constitute an excellent test, due to their known sensibility to simulation details as equilibration and production time, sample size and adopted FF (Tiberco et al, private commun.) 3, 5–14. The origin of these requisites lies in the large dimensions of most mesogenic molecules, their slow dynamics and the strong dependence of LC phase stability from the chemical details of their forming molecules 15–18…”

Section: Introductionmentioning

confidence: 99%

Force‐field modeling through quantum mechanical calculations: Molecular dynamics simulations of a nematogenic molecule in its condensed phases

2008

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Interaction energy of the 4-n-pentyloxy-4'-cyanobiphenyl (5OCB) dimer is computed at MP2 level, for many geometrical arrangements using the Fragmentation Reconstruction Method (FRM). DFT calculations are performed for a number of geometries of the monomer. The resulting database is used to parameterize an atomistic intra- and inter-molecular force-field suitable for classical bulk simulations. Several structural and dynamical properties in 5OCB isotropic and liquid crystalline phases are computed from molecular dynamics simulation mainly in the NPT ensemble. Lengthy runs (more than 70 ns) and large sample sizes (up to 806 molecules) were used to determine the nematic to isotropic transition temperature up to a precision of few K. Good agreement was found in most of the investigated properties, thus validating the accuracy of the proposed model potential, only derived by quantum mechanical calculations.

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“…[4,9,13,15,16] Recently, a few simulations lasting up to 8 and 12 ns have appeared, [8,12] but these have involved the study of one, or very few, state points: again not sufficient to assess the ability of the methodology to predict transitions. The rather short runs are probably also connected to the contradictory preliminary findings on size dependence: thus in a recent study comparing N 118 and N 994 simulations, no size dependence was found: [18] in contrast to what was found on going from N 125 to 1000.…”

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confidence: 99%

Can Nematic Transitions Be Predicted By Atomistic Simulations? A Computational Study of The Odd–Even Effect

2004

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Computer simulations at the atomistic level are often called realistic as they offer, in principle, the possibility of reproducing in full the properties of a molecular system. Unfortunately, the number of atomic centers for molecules forming liquid-crystalline phases is normally so large, and correspondingly the number of molecules considered so low, that the proof of true realism, for example, the approximate reproduction of transition temperatures and of the relevant observables (such as order parameters together with their temperature dependence) has to our knowledge never been given to date. This is understandable in view of the complexity of liquid crystal molecules and probably depends on at least three issues: interaction potentials, sample size, and equilibration time. The force fields available have not been developed to reproduce liquid crystal properties, and only recently have some recommendations on the most appropriate choice amongst the many force fields available [1] been made. Sample sizes have varied from a number of particles N 50, [2±4] to 64 N 75, [5±10] to 100 N 125, [8, 11±15] and to N 200 molecules. [16] In a few recent cases, larger samples with N % 10 3 [17,18] particles have been simulated but without really studying the full temperature dependence and identifying transitions.At atomistic resolution, the observation time window in molecular dynamics (MD) calculations has also been quite short, ranging from less than % 600 ps [2, 3, 5±7, 10, 11, 14±18] to 1 or 2 ns. [4,9,13,15,16] Recently, a few simulations lasting up to 8 and 12 ns have appeared, [8,12] but these have involved the study of one, or very few, state points: again not sufficient to assess the ability of the methodology to predict transitions. The rather short runs are probably also connected to the contradictory preliminary findings on size dependence: thus in a recent study comparing N 118 and N 994 simulations, no size dependence was found: [18] in contrast to what was found on going from N 125 to 1000. [17] These strong limitations have been paralleled by the development of molecular-level models, where molecules are considered as simple objects, either just hard or endowed with attraction and repulsion, as in the Gay ± Berne models.[19] These approximate models have proven extremely useful in studying the general properties of liquid crystals (LC), such as phase transitions and correlations, and in discussing the existence of new and yet undiscovered phases such as the biaxial [20] and the ferroelectric nematic, [21] suggesting design hints to the synthetic chemist.However, there is a class of problems and observations that are very important for the understanding of anisotropic fluids, and completely depends on an atomistic level description. The foremost example is probably the prediction of the nematic ± isotropic (NI) transition temperature T NI , a crucial element in the design of viable LC display materials that have to exist and operate in a certain temperature range, that is now tackled empirically. [22,23...

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Molecular dynamics simulations of the bulk phases of 4-cyano-4′-n-pentyloxybiphenyl

Cited by 29 publications

References 43 publications

Stability of the nematic phase of 4-n-pentyl-4′-cyanobiphenyl studied by computer simulation using a hybrid model

Stability of the nematic phase of 4-n-pentyl-4′-cyanobiphenyl studied by computer simulation using a hybrid model

Force‐field modeling through quantum mechanical calculations: Molecular dynamics simulations of a nematogenic molecule in its condensed phases

Can Nematic Transitions Be Predicted By Atomistic Simulations? A Computational Study of The Odd–Even Effect

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